Spray coating, method of forming same, spray material wire, and cylinder block

ABSTRACT

An arc spray coating that is superior in both wear resistance and machinability, method of forming same, an arc spray wire used to form such a coating, and a cylinder block on whose bore inner surface is formed such an arc spray coating are provided. To this end, the arc spray coating contains Fe as a main component, 0.01% to 0.15% by weight of C, and at least 0.12% by weight of N, and the arc spray wire (wire) contains Fe as a main component, 0.01% to 0.2% by weight of C, and 0.25% to 1.7% by weight of Si, and may further contain at least 11% by weight of Cr as another embodiment.

TECHNICAL FIELD

The present invention relates to a cylinder block of an engine, a spraycoating formed on the bore inner surface of the cylinder block and amethod of forming same, as well as a spray material wire for formingsuch a spray coating.

BACKGROUND ART

On cylinder bore inner surfaces of cylinder blocks, spray coatings forimproving the corrosion resistance, wear resistance, and the like of thebore inner surfaces are formed by thermal spraying techniques in which acombustion flame (flame) is generated by an arc, plasma, gas, or thelike, various metals and alloys are instantly melted, and sprayparticles that have been atomized (microparticulated) by compressed airare made to impact/solidify and adhere.

Incidentally, as wires for spraying (wires) used in arc spraying,ferrous material wires having a high carbon content are used in order toimprove the wear resistance of the spray coating. For example, withrespect to the spray materials disclosed in Patent Document 1, there isdisclosed a spray material comprising 0.3% to 2.0% by weight of C, 3% to20% of Cr, and 2% to 7% by weight of Si.

Improved wear resistance may be expected as the carbon content becomeshigher. On the other hand, machinability (reducibility of machining tipwear amount) becomes poorer (deteriorates), and a boring process using ahard tip, which is a finishing process for a spray coating, becomesdifficult. This reduction in machinability leads to a reduction in theyield of the spray coating process as a whole, and it also leads todegradation in the quality of the spray coating (dimensional toleranceof the spray coating is large). In addition, as the carbon contentincreases, the drawability of the arc spray wire becomes poorer. Thisleads to increased wire costs, the wires become more rigid, feedabilitythereof in the thermal spray apparatus becomes poorer, and wire feedingalso becomes difficult. On the other hand, it is clear that as thecarbon content decreases, the required hardness would not be obtained,and the coating would have poor wear resistance.

Therefore, with respect to arc spray coatings formed on cylinder boreinner surfaces, the development of an arc spray coating superior in bothits wear resistance and machinability, as well as the development of anarc spray wire for forming such a coating have been urgent problems inthe field.

Patent Document 1

-   Japanese Patent Publication (Kokai) No. 2004-244709 A

DISCLOSURE OF THE INVENTION

The present invention is made in view of the problems above, and itsobject is to provide an arc spray coating that is superior in both wearresistance and machinability, a method of forming same, an arc spraywire used in forming such a coating, and a cylinder block in which suchan arc spray coating is formed on the bore inner surface thereof.

In order to achieve the object above, an arc spray coating according tothe present invention is characterized in that it contains Fe as a maincomponent, 0.01% to 0.15% by weight of C, and at least 0.12% by weightof N.

An arc spray coating of the present invention is suitable for beingformed on the bore inner surface of a cylinder block of an engine.However, besides bore surfaces of cylinder blocks, it may also be formedon internal surfaces of appropriate tubular members for which it isnecessary to improve the wear resistance and the like thereof, such asthe sliding surface of a cylinder constituting a cylinder unit mechanismthat is an actuator.

This arc spray coating is formed of iron alloy particles whose maincomponent is Fe (pure iron), and which contains, where the coating as awhole is 100% by weight, 0.01% to 0.15% by weight of C (carbon), and atleast 0.12% by weight of N (nitrogen).

Here, the carbon content range mentioned above is a range forsimultaneously giving the arc spray coating the desired hardness (wearresistance) as well as the desired machinability. As compared toconventional arc spray coatings which are designed to improve wearresistance only, the carbon content range thereof is set to a lowerrange. Desired machinability as used herein may be defined in terms of,for example, the wear amount of the flank face when a boring process orthe like is performed on the arc spray coating with a hard tip.

When the carbon content is less than 0.01% by weight, the coating is toosoft, and a predetermined wear resistance cannot be achieved. Inaddition, once the carbon content exceeds 0.15% by weight, the wearamount of the flank face mentioned above becomes greater during theboring process. Further, it becomes impossible to use thelater-described commercially available arc spray wires, thereby causingcoating quality degradation and a sharp rise in processing cost.

The desired wear resistance mentioned above is achieved by having notonly carbon of the above-mentioned content range contained, but alsonitrogen of the above-mentioned content range. This nitrogen is thenitrogen that is present in the air, and is incorporated into theatomized spray particles. The present inventors have discovered the factthat the wear resistance of spray coatings improves by having nitrogenof the above-mentioned content range. Here, the desired wear resistancemay be defined in terms of the depth of wear of the arc spray coating.For example, a comparable or lesser depth of wear to or than that of acast iron liner cast into the cylinder bore may be set as a referencevalue.

An arc spray coating of the present invention is one in which the carboncontent and the nitrogen content have been so adjusted to satisfy boththe desired wear resistance and machinability. It at least has a wearresistance comparable to that of a cast iron liner, and also allows foran efficient implementation of a boring process. Therefore, theprocessing accuracy of the ultimately formed coating surface is alsosuperior, and it is possible to obtain a sliding surface with highdurability.

In addition, an arc spray wire according to the present invention is anarc spray wire for forming the above-mentioned arc spray coating, and ischaracterized in that it contains Fe as a main component, 0.01% to 0.2%by weight of C, and 0.25% to 1.7% by weight of Si.

According to experiments by the inventors, it has been substantiatedthat, as components of an arc spray wire (wire) for forming an arc spraycoating comprising Fe as a main component, 0.01% to 0.15% by weight ofC, and at least 0.12% by weight of N, first, 0.01% to 0.2% by weight ofcarbon is required as the carbon content of a wire for realizing theabove-mentioned carbon content in the coating, and that 0.25% to 1.7% byweight of silicon is required as the silicon content of a wire forrealizing the above-mentioned nitrogen content in the coating.

During spraying, an arc spray wire is fed, and this is melted andatomized. However, when the carbon content of the arc spray wire is lessthan 0.01% by weight, the wire buckles during wire feeding, and sprayingprocessability is severely compromised. On the other hand, once thecarbon content of the wire exceeds 0.2% by weight, the carbon content ofthe spray coating exceeds 0.15% by weight, thereby impairing themachinability of the spray coating.

In addition, when the silicon content is less than 0.25% by weight, thebond strength of the arc spray coating to the bore inner surface becomesextremely low, and once it exceeds 1.7% by weight, the nitrogen contentin the arc spray coating becomes less than 0.12% by weight, therebycompromising the wear resistance of the coating. In other words, thepresent inventors have discovered that the silicon content in the arcspray wire plays an important role in incorporating a predeterminedamount of nitrogen from air.

In addition, a preferred embodiment of an arc spray wire according tothe present invention is characterized in that at least 11% by weight ofCr is further contained in addition to the contained components of thewire mentioned above.

According to experiments by the present inventors, it has beendiscovered that an effect may be achieved where the nitrogen content inthe formed coating is increased when the above-mentioned wire contains11% by weight or more of chromium. It is noted that this effect cannotbe expected when the chromium content is less than 11% by weight.Therefore, a predetermined nitrogen content is secured by the siliconcontained in the wire. It is noted that once the chromium contentexceeds 20% by weight, a sufficient hardness can no longer be achievedfor the spray coating due to an increase in ferrite. Therefore, it ispreferable that the contained amount thereof be 11% by weight or greaterbut less than 20% by weight.

By forming atomized particles using an arc spray wire of the presentinvention mentioned above and applying them to a bore surface, it ispossible to reliably form an arc spray coating having superior wearresistance and machinability, as well as superior bond strength withrespect to the bore surface.

Further, a method of forming an arc spray coating according to thepresent invention is characterized in that it comprises: a first step ofpreparing an arc spray wire containing Fe as a main component, 0.01% to0.2% by weight of C, and 0.25% to 1.7% by weight of Si; and a secondstep of melting the arc spray wire with a combustion flame, and formingon a cylinder bore inner surface an arc spray coating, which contains Feas a main component, 0.01% to 0.15% by weight of C, and at least 0.12%by weight of N, while supply compressed air to the molten arc spraywire.

More specifically, the arc spray coating is formed by making the surfaceroughness of the spray coating be at or below a certain roughness levelby performing a honing process after the first step and the second stepmentioned above. It is noted that the surface roughness of the coatingimmediately after arc spraying may, in some cases, be extremely highsuch as an R_(max) of approximately 180. When a honing process(polishing process) that uses a diamond wheel or a CBN wheel isperformed thereon, there is a risk where the central axis of the honingprocess tool may become displaced, and unevenness in thickness may occurin the coating after the process. Thus, in such cases, by performing aboring process (cutting process) by means of a CBN cutter bit prior tothe honing process, the surface roughness of the coating may be keptbelow a certain level, and the problem of the occurrence of unevennessin thickness may be resolved by thereafter performing the honingprocess.

It is noted that, for the arc spray wire used, a wire containing 11% byweight or more of chromium as described above may naturally be used.

As can be understood from the description above, according to a spraycoating, a method of forming same, and a spray material wire of thepresent invention, it is possible to form an arc spray coating that hassuperior wear resistance and machinability, and that even has superiorbond strength with respect to a bore surface. Therefore, by producing acylinder block on whose bore surface is formed such a spray coating, itis possible to improve the durability thereof, and it leads to reducedproduction costs as a result of increased production yield thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a thermal spray apparatus.

FIG. 2 is an enlarged view of a spray gun.

FIG. 3 is a view of FIG. 2 in the direction of arrow

FIG. 4 is graph showing experiment results for determining the carboncontent in an arc spray coating, and is a graph relating to the flankface wear amount of coatings and carbon content.

FIG. 5 is a cross-sectional photograph and a profile photograph of anarc spray coating after a cutting process, whose carbon content is 0.05%by weight, and a cross-sectional photograph and a profile photograph ofan arc spray coating after a cutting process, whose carbon content is0.50% by weight.

FIG. 6 is a graph showing experiment results for determining thenitrogen content in an arc spray coating, and is a graph relating to thedepth of wear of coatings and nitrogen content.

FIG. 7 is a graph showing experiment results for determining the carboncontent in a wire, and is a graph relating to the carbon content inwires and the carbon content in coatings.

FIG. 8 is a graph showing experiment results for determining the siliconcontent in a wire, and is a graph relating to the silicon content inwires and the nitrogen content in coatings.

FIG. 9 is a graph showing experiment results for determining the siliconcontent in a wire, and is a graph relating to the silicon content inwires and the bond strength of coatings with respect to a bore surface.

FIG. 10 is a graph showing experiment results for determining thechromium content in a wire, and is a graph relating to the chromiumcontent in wires and the nitrogen content in coatings.

In the figures, 1 denotes a base, 2 a support portion, 3 a spray tool, 4a controller, 51 an ascent/descent drive motor, 52 a rotation drivemotor, 6 a spray gun, 61 a tip member, 62 an atomizing nozzle, 63 anauxiliary nozzle, 7 a palette, 10 a thermal spray apparatus, C acylinder block, C1 a bore, A1 auxiliary air, and A2 atomizing air.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention is described below with referenceto the drawings. FIG. 1 is a schematic view showing a thermal sprayapparatus. FIG. 2 is an enlarged view of a spray gun. FIG. 3 is a viewof FIG. 2 in the direction of arrow III-III. FIG. 4 is a graph showingexperiment results for determining the carbon content in an arc spraycoating, and is a graph relating to the flank face wear amount ofcoatings and carbon content. FIG. 5 is a cross-sectional photograph anda profile photograph of an arc spray coating after a cutting process,whose carbon content is 0.05% by weight, as well as a cross-sectionalphotograph and a profile photograph of an arc spray coating after acutting process, whose carbon content is 0.50% by weight. FIG. 6 is agraph showing experiment results for determining the nitrogen content inan arc spray coating, and is a graph relating to the depth of wear ofcoatings and nitrogen content. FIG. 7 is a graph showing experimentresults for determining the carbon content in a wire, and is a graphrelating to the carbon content in wires and the carbon content incoatings. FIG. 8 is a graph showing experiment results for determiningthe silicon content in a wire, and is a graph relating to the siliconcontent in wires and the nitrogen content in coatings. FIG. 9 is a graphshowing experiment results for determining the silicon content in awire, and is a graph relating to the silicon content in wires and thebond strength of coatings with respect to a bore surface. FIG. 10 is agraph showing experiment results for determining the chromium content ina wire, and is a graph relating to the chromium content in wires and thenitrogen content in coatings.

FIG. 1 is a schematic view of an embodiment of a thermal spray apparatusthat is used in forming an arc spray coating of the present invention ona bore inner surface of a cylinder block. This thermal spray apparatus10 substantially comprises: a base 1; a support portion 2 that issupported by and fixed to the base 1; a spray tool 3 that slides up anddown along the support portion 2; a spray gun 6 that is installed at thetip of this spray tool 3; a controller 4; and a palette 7 that acylinder block C is to be placed on and fixed to.

The support portion 2 is placed on the base 1, and supports a slider 31,which is provided on the spray tool 3, in a freelyascendible/descendible manner. The controller 4 is connected to anascent/descent drive motor 51, which is installed on the upper portionof the support potion 2, and a rotation drive motor 52. A helical screw32 is attached to a rotary shaft of the ascent/descent drive motor 51.The helical screw 32 is mated with a support 33 that is fixed to theslider 31. The controller 4 controls the rotation direction and rotationspeed of the ascent/descent drive motor 51. The spray tool 3 is able toascend and descend at a desired speed by means of the rotation of theascent/descent drive motor 51.

A tool main body 34 of the spray tool 3 has the spray gun 6 installed onits tip. The tool main body 34 and the spray gun 6 rotate about theiraxes (direction Y in the figure) by means of the rotation drive motor52. In addition, the palette 7 is installed on the base 1, and fixatesthe cylinder block C placed thereon. When the tool main body 34 and thespray gun 6 ascend/descend (direction X in the figure) within a bore C1of the cylinder block C in a rotating posture, spray particles aresprayed onto the bore surface of the bore C1. It is noted that thecylinder block C is formed from an aluminum alloy casting, and JISAC2C,ADC12 and the like, for example, may be used.

FIG. 2 is an enlarged view of the spray gun 6, and FIG. 3 is a side viewthereof. When the thermal spray apparatus 10 performs spraying, avoltage is applied to power lines not shown in the figures. An arc isgenerated at the tip contact portion of arc spray wires (wires W). Dueto the heat therefrom, the tips of the wires W melt. An amount of thewires W that has been melted and consumed is drawn out and fed from areel by means of rotation of a feed roller not shown in the figures.When air is supplied to a hose not shown in the figures, auxiliary airA1 blows out from an auxiliary nozzle 63, while atomizing air A2 blowsfrom an atomizing nozzle 62 provided in a tip member 61 of the spray gun6 (see FIG. 3).

FIG. 2 schematically shows a state where the tips of the wires W havemelted, and the auxiliary air A1, which is compressed air, is blown outfrom the auxiliary nozzle 63. Here, the nitrogen components in the airare added into a droplet W1, and a predetermined nitrogen content isthus made to be contained in pure iron having a predetermined carboncontent.

In addition, as shown in FIG. 3, the atomizing air A2 that is blown fromthe atomizing nozzle 62 is blown onto the droplet W1. As a result, thedroplet W1 is dispersed into fine spray particles W2, . . . . Underthese conditions, when the spray tool 3 ascends or descends within thebore C1 of the cylinder block C at a predetermined speed while rotatingthe spray gun 6, the spray particles W2, . . . are sprayed onto theinner surface of the bore C1. The sprayed spray particles W2, . . .adhere to the inner surface of the bore C1 to form a spray coating.

Experiments, and the results thereof, for determining the containedcomponents forming an arc spray coating material of the presentinvention and the contained amounts thereof, as well as the containedcomponents forming a wire for forming such a spray coating and thecontained amounts thereof, are described in detail below.

[Experiment for Determining the Carbon Content in an Arc Spray Coating,and Results Thereof]

An arc spray coating of the present invention comprises an alloyed ironpowder of main component Fe—C—N. First, an experiment for determiningthe carbon content will be described. In forming a spray coating that issuperior not only in wear resistance but also in machinability, itscarbon content will be determined from the viewpoint of machinability inparticular. As will be described later, this is because it is possibleto effectively form a spray coating that is superior in both performancecharacteristics of wear resistance and machinability by determining thecarbon content in such a manner as to satisfy a predetermined level ofmachinability performance, and determining a predetermined level of wearresistance performance by way of the nitrogen content based on thiscarbon content.

The testing method was such that fifty cast iron liners with an innerdiameter of 82 mm were prepared instead of cylinder blocks, and fiftyarc spray coatings of a thickness of 0.45 mm were consecutively formedon the inner surfaces of the respective cast iron liners. Thereafter,the flank face wear amounts from boring processes performed on theformed spray coatings were measured to assess machinability. It is notedthat the specific processing conditions of the boring process were thata dry cutting process was performed with a grinding apparatus having acutting tip comprising 80% by weight of CBN as the grinding apparatus atrotation speed: V=600 m/min, feed=0.3 mm/rotation, and depth of cut: 0.3mm Results thereof are shown in Table 1 and FIG. 4.

TABLE 1 Carbon Content (% by weight) Quantity Flank Face Wear AmountWire Spray Coating Processed (mm) 0.06 0.05 50 0.045 0.20 0.15 50 0.0550.32 0.23 50 0.12 0.61 0.45 15 0.32 0.79 0.50 15 chipping

Table 1 shows the carbon content in the corresponding wire in additionto the carbon content in the spray coating. Here, the wire whose carboncontent is 0.20% by weight is one that is widely sold in general,examples of which include JIS SWRM 20K, 22K and the like. By using thiscommercially available wire, it is possible to make the production costof the coatings cheaper. Therefore, the present inventors adopted as thecarbon content of the spray coating the carbon content of 0.15% byweight (<content: 0.20% by weight calculated from the reference value)in the spray coating formed when this wire with a Carbon content of0.20% by weight was used.

It is noted that when the carbon content of the spray coating was madeto be 0.50% by weight, chipping occurred in all fifteen test cast ironliners. This is because the coating itself became brittle due toexcessive carbon contents.

FIG. 5 shows cross-sectional photographs (left) and profile photographs(right) of coatings after testing with respect to a spray coating with acarbon content of 0.05% by weight (working example) and a spray coatingwith a carbon content of 0.50% by weight (comparative example). As isapparent from the photographs, whereas chipping is present in thecoating in the comparative example, a smooth coating surface is formedin the working example.

[Experiment for Determining the Nitrogen Content in an Arc SprayCoating, and Results Thereof]

Next, a block was attached to a jig with an inner diameter of 82 mmcompliant with ASTM D2714, and arc spraying using various wires havingthe compositions shown in Table 2 below was performed. After arcspraying, a polishing process was performed and a sliding test wasperformed. Here, the wire feed rate during spraying was 100 mm/sec, wirediameter was φ 1.6 mm, and the applied voltage was 30 V. In addition,the carbon content of each wire was adjusted to 0.15% by weight orbelow. The nitrogen content in the coating formed when each wire wasused is indicated in Table 2. The depth of wear was measured for thecoating of each nitrogen content, and the result thereof is shown inTable 2 and FIG. 6.

TABLE 2 Wire Composition Coating Composition Bond Strength (% by weight)(% by weight) Depth of (normalized C Si Mn Cr C N Wear (μm) value)Material A 0.05 1.95 0.43 0.03 0.08 20 0.98 Material B 0.06 1.71 1.860.04 0.12 9.6 1 Material C 0.06 1.47 0.38 0.05 0.13 8 1.03 Material D0.06 0.84 1.39 0.05 0.14 7 0.95 Material E 0.08 0.25 1.10 0.01 0.05 0.156.5 1 Material F 0.12 0.02 1.91 0.06 0.20 7 0.55

With respect to bond strength, it is noted that the bond strength ofmaterial B is taken to be 1, and the strengths of others are normalized.In FIG. 6, 12 μm, which is the depth of wear of the cast iron liner, isindicated as a reference value in the present experiment. From theexperiment, it was substantiated that the nitrogen content range in thecoating for which the depth of wear was less than the referential 12 μmwas 0.12% by weight or above for arc spray coatings whose carbon contentin the coating was adjusted to 0.15% by weight or below.

[Determination of the Carbon Content and Silicon Content in a Wire,Experiment for Determining the Silicon Content, and Results Thereof]

First, the carbon content in a wire for forming a coating, whose carboncontent would be 0.15% by weight or less, can be determined by formingarc spray coatings using various wires of which the carbon content isvaried. Such experiment results are shown in FIG. 7.

From FIG. 7, it has been substantiated that the formation of a coatingwhose carbon content is 0.15% by weight or less can be realized bysetting the carbon content in the wire to 0.2% by weight or less.

On the other hand, through experiments by the present inventors usingwires with varying silicon contents, it has been substantiated that apredetermined amount of silicon contained in the wire plays an importantrole when the spray coating incorporates a predetermined amount ofnitrogen from the air. This can be explained based on Table 2 above andFIG. 8. To explain Table 2 again, the compositions of the respectivewires used are such that the silicon content is varied within a range of0.43% to 1.91% by weight under conditions where the carbon content iskept substantially constant.

From the experiment, it was substantiated that the nitrogen content inthe formed coating can be made to be 0.12% by weight or above astargeted by adjusting the silicon content to 1.7% by weight or below.Therefore, the upper limit value for the silicon content in the wire maybe defined at 1.7% by weight.

On the other hand, the lower limit value of the silicon content in thewire may be defined from the bond strength of the formed coating withrespect to the bore inner surface. The present inventors performed bondstrength tests therefor. Briefly, in the experiment, an ADC 12 cylinderblock having a cylinder bore with an inner diameter of 82 mm was formed,and arc spraying was performed using each wire with a wire diameter of φ1.6 mm whose composition is indicated in Table 2 above, at a feed rateof 100 mm/sec and an applied voltage of 30 V.

The bond strength was assessed by cutting out a coating specimen fromthe bore, and measuring the strength when this coating was sheared. Thetest results are shown in Table 2 and FIG. 9. It is noted that, in thetest results, the bond strength of the specimen from when material B,where the silicon content of the wire is approximately 1.7% by weight,was used was taken to be 1, and the results for the specimens by otherwires were normalized.

In the experiment, the bond strength of the coating dropped sharply whenthe silicon content in the wire was less than 0.25% by weight, and thevalues thereof were substantially the same at or above 0.25% by weight.From these experiment results, by defining the lower limit value of thesilicon content in the wire at 0.25% by weight, it becomes possible tomaintain the bond strength of the coating with respect to the boresurface at or above a certain level.

[Experiment for Determining the Chromium Content in a Wire, and ResultsThereof]

The present inventors focused on the chromium content in a wire as afactor that increases the nitrogen content in the spray coating, andexamined the nitrogen content of coatings formed using wires havingcompositions in which the carbon content is 0.2% by weight or below, thenitrogen content is 0.25% to 1.7% by weight, and the chromium content isin the range of 0% to 13.2% by weight. It is noted that the experimentconditions here are the same as those for the experiment above fordetermining the silicon content. The wire compositions used in thisexperiment and the experiment results are shown in Table 3 below and inFIG. 10. It is noted that, as methods for analyzing coating compositionsin Table 2 and Table 3, carbon is by JIS G 1211 iron and steel—methodsfor determination of carbon content (infrared absorption method aftercombustion in a high-frequency induction furnace), silicon is by JIS G1212 iron and steel—methods for determination of silicon content,manganese and chromium are by JIS G 1258 iron and steel—inductivelycoupled plasma atomic emission spectrometric method, and nitrogen is byJISG1228 iron and steel—methods for determination of nitrogen content.

TABLE 3 Wire Composition Coating Composition (% by weight) (% by weight)C Si Mn Cr C N Material E 0.08 0.25 1.10 0 0.05 0.15 Material G 0.080.40 0.85 2.7 0.06 0.15 Material H 0.08 0.36 1.53 9.2 0.06 0.15 MaterialI 0.11 0.41 0.35 10.9 0.06 0.21 Material J 0.12 0.45 0.52 13.2 0.06 0.21

From the experiment, it was substantiated that the nitrogen content inthe coating increases by approximately 40% in the 9% to 11% by weightrange of chromium content. From these results, it was concluded that atleast 11% by weight of chromium should be contained in the wire in orderto increase the nitrogen content in the coating.

Embodiments of the present invention have been described in detail abovewith reference to the drawings. However, specific configurations are notto be limited to these embodiments, and even if design changes and thelike are made within a scope that does not depart from the spirit of thepresent invention, they are to be included in the present invention.

1-2. (canceled)
 3. An arc spray wire for forming an arc spray coatingcomprising Fe as a main component, 0.01% to 0.15% by weight of C, and atleast 0.12% by weight of N, wherein the N had been present in the airand incorporated into atomized spray particles, the arc spray wirecomprising Fe as a main component, 0.01% to 0.2% by weight of C, and0.25% to 1.7% by weight of Si.
 4. An arc spray wire for forming an arcspray coating comprising Fe as a main component, 0.01% to 0.15% byweight of C, and at least 0.12% by weight of N, wherein the N had beenpresent in the air and incorporated into atomized spray particles, thearc spray wire comprising Fe as a main component, 0.01% to 0.2% byweight of C, 0.25% to 1.7% by weight of Si, and at least 11% by weightof Cr.
 5. (canceled)